#单分支if语句
score = eval(input('请输入成绩分数'))
if score >= 60:
    print("成绩已合格")


score = eval(input('请输入成绩分数'))
if score < 60:
    print("成绩不合格")
if 60 <= score < 80:
    print("成绩一般")
if 80 <= score <= 90:
    print("成绩良好")
if 90 < score <= 100:
    print("成绩优秀")


score = eval(input('请输入成绩分数'))
if 60 <= score:
    print("成绩已合格")
    if 90 <score <= 100:
        print("成绩优秀")

        
a = 50
if a > 20:
    print("变量a大于20")
else:
    print("变量a不大于20")

score = eval(input("请输入成绩分数"))
if score >= 60:
    print("成绩及格")
    if score >= 90:
        print("成绩很好")
    else:
        print("成绩一般")

score = eval(input("请输入成绩分数"))
if score >= 60:
    print("成绩及格")
    if score >= 90:
        print("成绩很好")
    else:
        print("成绩一般")
else:
    print("成绩不及格")
    if score < 30:
        print("成绩极差")
    else:
        print("成绩较差")

score = eval(input("请输入成绩分数"))
if score >= 90:
    print("成绩优秀")
elif score >= 80:
    print("成绩良好")
elif score >=70:
    print("成绩中等")
elif score >= 60:
    print("成绩较好")
else:
    print("成绩不合格")

a = eval(input("输入一个年份"))
if a % 4==0 and a % 100!=0 or a % 400==0:
    print("是闰年")
else:
    print("不是闰年")


a = 1
while a <= 100:
    print("今天是第", a)
    a = a + 1

n = 1
sum = 0
while n <= 100:
    sum = sum + n
    n = n + 1
    # print(sum)
print(sum)

for i in 'python':
    print(i)

for i in range(10):
    print(i)
    print()



 #嵌套循环
i = 1
while i <= 5:
    print("上班星期为：",i)
    i = i+1
    t = 9
    while t <= 17:
        print("时间段：",t,end="")
        t = t+1
    print()

for i in range(1,6):
    print('上班为周：',i)
    for t in  range(9,18):
        print('时间段为：', end="")
    print()

#九九乘法表
i = 1
while i <= 9:
    j = 1
    while j <= i:
        print('%d*%d=%d' % (j, i, j*i), end=" ")
        j = j + 1
    print()
    i = i + 1

    

for i in range(1,10):
    for j in range(1,1+i):
        print('%d*%d=%d' % (j, i, j*i), end=" ")
    print()


    
# while 中使用break跳出循环
i = 0
while i <= 5:
    i += 1
    print('星期为：', i)
    if i == 3:
        break

i = 0
while i <= 5:
    if i == 3:
        break
    print('星期为：', i)
    i += 1

# for循环中使用break语句
for i in range(1, 6):
    print("星期", i)
    if i == 3:
        break

for i in range(1, 6):
    if i == 3:
        break
    print("星期", i)

# while循环中使用continue语句
i = 1
while i < 5:
    i = i + 1
    if i == 4:
        continue
    print("星期", i)

# for循环中使用continue语句
for i in range(1, 6):
    if i == 4:
        continue
    print("星期", i)


    # while 中使用break跳出循环
i = 0
while i <= 5:
    i += 1
    print('星期为：', i)
    if i == 3:
        break

i = 0
while i <= 5:
    if i == 3:
        break
    print('星期为：', i)
    i += 1

# for循环中使用break语句
for i in range(1, 6):
    print("星期", i)
    if i == 3:
        break

for i in range(1, 6):
    if i == 3:
        break
    print("星期", i)

# while循环中使用continue语句
i = 1
while i < 5:
    i = i + 1
    if i == 4:
        continue
    print("星期", i)

# for循环中使用continue语句
for i in range(1, 6):
    if i == 4:
        continue
    print("星期", i)